Method for bleaching oil with adsorbent



Nov. 18, 1952 I A, E. BAlLEY 2,618,644

METHOD FOR BLEACHING OIL WITH ADSOR BENT:

Filed Nov. 4. 1948 2 SHEETS -SHEET 1 VACUUM INVENTOR Patented Nov. 18, 1952 METHOD FOR BLEACHING OIL WITH ADSORBENT Alton E. Bailey, Louisville, Ky., assignor to The Girdler Corporation, Louisville, Ky., a corporation of Delaware Application November 4, 1948, Serial No. 58,327

7 Claims.

This invention relates to bleaching of oils, and the method of the invention is applicable to both fatty oils and petroleum oils. Certain aspects of the method are of especial advantags in the bleaching of fatty oils, for reasons which will be apparent as this description proceeds.

The method of the invention utilizes a bleaching adsorbent, such as carbon black or bleaching clays, for example, fullers earth. One of the most important objects of the invention is to increase the efficiency of bleaching. At the same time the invention has in view reducing oil losses incident to the bleaching operation.

The foregoing important general objects are obtained according to the invention by employment of a method which may be continuously operated and which at the same time utilizes the principle of counterflow with respect to the use of the adsorbent employed in bleaching the oil.

The invention makes possible the attainment of a given degree of bleaching, with the employment of substantially less adsorbent than has been practicable heretofore, this being of great importance for the reason that oil losses are thereby correspondingly reduced.

In considering certain other objects and advantages of the invention, it is first noted that oils to be bleached frequently contain occluded or dissolved air and/or moisture; and also that adsorbents commercially available for bleaching operations similarly include occluded air and/or moisture, and also bound moisture. The presence of air or oxygen at the temperatures required for effective bleaching is undesirable because of resultant oxidation and degradation of the oil. In addition, the presence of moisture at the bleaching temperatures is undesirable in the bleaching of fatty oils for the reason that moisture tends to split the fatty oil molecule,

thereby producing free fatty acids. Any appreciable content of free fatty acid is objectionable in fatty oils, especially where such products are to be utilized in the preparation of food products.

With the foregoing in mind, the invention provides a method which is not only capable of continuous operation and which utilizes the counterflow principle with reference to contact of the oil with the bleaching adsorbent, but 1 which still further makes provision for separation of both air and moisture from both the oil and the adsorbent prior to any prolonged period of heating of the oil.

How the foregoing and other objects and advantages are attained-will appear more fullyfrom the following description referrin'g to'the accompanying drawingsin' which- 1 Figure 1 is a schematic view' of one system capable of carrying out the method 'of the invention;

Figure 2 is a view similar to Figure 1 but illustrating certain modifications which may be employed; and

Figure 3 is a schematic view of another systerm for carrying out the methodo'f the inven: tion, provision here being made for certain ad ditional treatment steps'not provided for in the systems of Figures 1 and 2. H H p The primary components of the system shown in Figure 1 include a treatment column generally indicated at C, in which various treatment steps are eiiected; a battery of filter presses of the closed delivery type generally indicated at F 15 and F a clay and oil mixing vessel indicated at M, a clay supply indicated at S, and a vacuum system V withconnections to column C, vessel M and supply tank S. v

Oil to be treated is delivered to the system and first introduced through a pipe 4 terminat ing in a spray nozzle or the like, so as to deliver a spray of oil into the upper chamber 5 of the treatment column 0. The oil is here passed in counterflow with stripping steam introduced at 6.from a steam supply line I, the steam and volatile matter being withdrawn from the top of the chamber 5 through the vacuum connection referred to. This treatmentis effective to remove, occluded and dissolved air and moisture carried by the oil.

The oil accumulates in the bottom of chamber 5'and is withdrawn through connection 8 and is pumped through the heat exchanger E in which the oil receives heat from oil circulating" in another portion of the system. Additional heat is supplied to the'oil by means of the heater H, which may appropriately be heated 'by steam. The connection 8 is provided with three valved branches 8a, 3b and 8c delivering respectively to the three filter presses F F and F Assuming for the moment that branch 8a is open and branches 8b and 8c are closed and that the filter F contains a cake or mass of adsorbentitwill be seen that the heated oil is passed through the mass of adsorbent in the filter F and is thereby partially bleached. As will further appear here inafter, the adsorbent present in filter F comprises partially spent adsorbent which has previously been used in another bleaching stage of the method.

Each of the filter presses has an oil'discha rge connection shown at 9a. 9b and 90, which are valved for selective delivery to the pipe 9. Assuming for the moment that connections 9b and 9c are closed and connection 9a open, the filtered and partially bleached oil is delivered from press F through pipe 9 into the clay and oil mixing vessel M. Here the oil is mixed with fresh adsorbent fed from the supply tank S, an agitator l serving to intimately admix the fresh adsorbent with the oil. The resulting slurry is withdrawn from the bottom of vessel M through the connection I l and is pumped'through asupply or equivalent nozzle located in the lower treatment chamber l2 of the treatment column C. Here the finely divided mixture oi oil and adsorbent is passed in counterfiow with stripping steam introduced at l3, the steam and volatile matter flowing upwardly through the center Qhan e1..;l4 which provid s communic ti n. etween theilower and upper chambers 12 and-5 of the treatment column. This steam and the volatiles ;pa ss out through the vacuum connection at-the top of the column.

The clay and oil mixing vessel M is provided with a heating jacket 15 by which the temperature of the oil is raised to an effective bleaching temperature, and in view of this the oil and clay mixture sprayed into the chamber 12 is also at'high temperature, in consequence of which bound moisture in the clay is released and is carriedawaywith the steam and other volatile matter.

At this point attention is further called to thefact that the clay supply tank-S is provided with aconnection with the vacuum system, in

view of which the clay is subjected to deaeration prior'to introduction into the clay and oil mixing vessel'M.

-The oil iswithdrawnfrom the lower chamber 12. of the treatment column through the pipe 45 and is pumped to one or another of the filter presses through one of the valved connections Isa; l6b and IE0. Assuming that valve I62) is open and-valves 16a and I60 are closed, the mixture of oil andadsorbent is delivered to the filter press -F ,-in which the adsorbent is separated from the oil, remaining as a cake in the filter press.

From the above it will be seen that a second stage of bleaching of the oil has now been effected. The bleached oil is delivered from press 1*" through the connection 91) and thence throughthevalved connection 11b to the pipe l1. Similar valved connections [1a and We serve to interconnect presses. F and F with the pipe ll. Theheatedoil in pipe [1 now fiows'through the exchanger-E, inheat exchange relation with the oil in pipe 8. Prior to discharge'of the bleached oil, itprnay'be subjected to further cooling in a cooler indicatedat l8, which may desirably employ water as' a cooling medium, to thereby reducethe-temperature of the oil below oxidation temperature, prior to ultimate delivery to storage, and exposure of the oil to the atmosphere.

It is contemplated in the operation of the system above described that after build-up of an appreciable cake of adsorbent in filter press E the flow from line l6 should be diverted to filter press F by closing valves I62) and [1b and opening valves I60 and Ho. It is further contemplated that the oil flow in line 8 then be shifted from filter press F to filter press F by appropriate manipulation of the valves in connections 8a-9a and 8b-9b. In this way, the adsorbentwnow .in filter press F which had been used for the second stage of bleaching is re-used for the first stage of bleaching. Upon changing the adjustment of the valves as above described, a new cake of partially spent adsorbent will be built up in filter press F The twice-used adsorbent remaining in filter press F is now discarded. By employing at least three filter presses in the system as described, one of the presses is always out of operation to provide for cleaning-thereof, while the other two are being used respectively in connection with the first. and second stages of bleaching. Thus the system provides for continuous operation, notwithstanding the stepwise counterfiow employment of the adsorbent.

Several additional important points should be noted with respect to the system as above described.

First, the spraying of the incoming oil' into chamber 5 of the treatment column effectively separates air and moisture present in the oil, this being done at a temperature well below the temperature at which appreciable oxidation or splitting of the fatty oil molecules occurs. The oil is thereafter heated (by heaters E and H) to the desired bleaching temperature and is subjected to the first stage of bleaching by contact with the partially spent adsorbent utilized in the second bleaching step. Thereafter the oil is mixed, still out of contact with the air (because of the vacuum connection to the mixing vessel M), with fresh adsorbent which has previously been deaerated and the temperature of the mixture is again brought up to the effective bleaching temperature by the heating jacket l5. At this time bound moisture may be present in the adsorbent which is mixed with the oil, but such bound moiture is quickly removed by spraying of the mixture into the chamber l2 of the treatment column, so that when the oil is withdrawn from the bottom of the chamber i2 it is delivered to the filter press in substantially moisture-free condition, this being of importance since the oil requires appreciable time to pass through the filter press. The delivery of the slurry from the mixing vessel M directly to the chamber 12 will also quickly separate any small amount of adsorbed air which may be introduced into the system with the fresh adsorbent, before appreciable oxidation of the oil can occur. If a continuous supply of dried and deaerated oil is available as from the vacuum drier of a continuous centrifugal alkali refining plant, the first spraying step may be omitted.

From the foregoing it will be seen that at no time in the process is the oil retained for any extended period of time in the presence of any appreciable quantity of air-or moisture. Oxidation and formation of'free fatty acids are therefore kept at a minimum, while at the same time provision is made for continuous operation and for employment of the adsorbent in counterfiow with the oil. Highly effective bleaching is effected by the system with considerably less adsorbent than heretofore required, with the attendant advantage of reduction in oil losses.

Turning now to the arrangement of Figure 2, it is first noted that in general, the system therein shown is similar to that of Figure 1 except that centrifuges are utilized instead of the filter presses of Figure 1, and except further that the adsorbent is employed in three counterfiow stages. In Figure 2, a treatment column C is again employed, it-being'here; assumed that this .5 column is the same as that described above with reference to Figure 1.

The oil is sprayed into the upper chamber of the column, being delivered thereto through pipe Hi. The oil then passes through pipe 20, through a heat exchanger 2! and a heater 22, to a mixing device 23 in which the oil is intermixed with partially spent clay or adsorbent supplied to the device 23 as is indicated at 24. The mixture of oil and adsorbent is now carried by pipe 25 to the centrifuge 26, from which the oil is delivered through connection 21, the spent clay being discarded, as indicated at 28. Pipe 2i leads to a mixing device 29 in which the oil is intermixed with partially spent clay supplied as indicated at 30. The mixture-of oil and clay is delivered by connection 3| to the centrifuge 32. The clay taken out of the oil by the centrifuge 32 is that employed in the mixing device 23, as is indicated. The oil leaving centrifuge 32 is delivered through pipe 33 to the mixing device 3 in which the oil is intermixed with fresh adsorbent supplied from the receptacle 35. The slurry thus formed is delivered through connection it to the spray nozzle in the lower chamber of the treatment column 0. From this lower chamber the oil is discharged at 31 and is delivered to the centrifuge 38 which supplies clay to the mixing device 29, as is indicated. The oil leaving centrifuge 38 through pipe 39 is employed to partially heat the oil-flowing in line 20, as by means of the heat exchanger 2| above referred to.

Asin the arrangement of Figure 1, the system of Figure 2 provides for continuous flow and treatment of the oil, nothwithstanding the utilization of the adsorbent in counterflow and stepwise. Various of the other advantages and features of operation described above with reference to Figure 1 are also attained in the system of Figure 2.

Turning now to the system of Figure 3, it is first mentioned that this arrangement incorporates all of the features of Figure 1, together with some additional features which will be pointed out in the following description.

In the system of Figure 3 a treatment column is again employed, this being indicated at C the column here utilized being provided with three superimposed treatment chambers 66, and 42. Three filter presses F F and F are also employed in this arrangement, in the same general manner as described above with reference to Figure 1. Here also an adsorbent or clay and oil mixing vessel is provided as indicated at M, and a clay supply as shown at S. A vacuum system V serves to provide the desired reduced pressure in the treatment column and also to evacuate the clay supply tank S and the mixing vessel M.

Oil entering the system of Figure 3 is first fed through pipe 43 into a mixing vessel M in which the oil is admixed with adsorbent delivered from the supply tank S. For reasons which are discussed herebelow, this initial intermixing of the oil with adsorbent may or may not be utilized, depending upo certain factors to be mentioned. However, when this feature is employed, the mixture of oil and adsorbent is-delivered through pipe 44 into the uppermost chamber of the treatment column 0 in which it is preferably subjected to steam stripping as in Figure 1. Oil leaves the bottom of the chamber 40 through conneotion 45 and 'is'delivered through a heater t8 which'mayi be heated by'means .of steam or other suitable heating medium. From the heater 46 6. the oil is sprayed into'the intermediate chamber 4| of the treatment column.

Because of the sequential spraying of the oil into the two upper chambers of the treatment column, and because of the heating of the oil intermediate the two spraying operations, provision is made for initial treatment of the oil under reduced pressure (and preferably 3,150 in the presence of strippin steam) at a relatively low temperature, so as to deaerate both theoil and the adsorbent and to remove moisture therefrom, Upon leaving the heater 46 and delivery to the intermediate chamber 4|, the temperature has been raised sufficiently so that in chamber M bound moisture if present in the adsorbent is released and carried away through the vacuum connection at the top of the treatment column. The oil and adsorbent are now withdrawn from chamber 4! through pipe 41 and the mixture is delivered to one or another of the filter presses, for instance'filter press F valved branches i'la, Mb and 410 being provided for this purpose. Oil from filter press F is delivered through valved branch 48a to the pipe 48 which leads to the mixing vessel M in which the oil is intermixed With fresh adsorbent supplied from the tank S. As in the operation of the arrangement of Figure 1, it is contemplated that the first stage of bleaching of the oil referred to shortly above shall be effected by How of the oil through a mass or cake of partially spent adsorbent present in the filter press F Mixture of the oil with fresh adsorbent in the mixing vessel M now initiates the second stage of bleaching, the temperature being raised to or retained at the desired bleaching temperature as by a heating jacket 69 surrounding the lower portion of the mixing vessel M.

Oil is delivered from the mixing vessel M through the connection 50 and is sprayed into the bottom chamber 42 of the treatment column, this operation serving the same function as described above with reference to Figure 1, i. e., the release of bound moisture present in the fresh adsorbent. The oil is withdrawn from the bottom of chamber 82 through the connection 5! and is delivered through one or another of the branches 51a, Ella and 510 to one of the filter presses, for instance, press F This filter press separates-the adsorbent used in the second stage of bleaching and the oil is discharged to line 52, through one or another of thevalved branches 52a, 52b and 520. Line 52 leads to a receiving tank or the like shown at 53, a cooler 54 being provided in this line if desired so as to lower the temperature of the oil to a point well below oxidation temperature, prior to ultimate delivery of the oil out of the system.

For purposes of cleaning various parts of the system, a clean-out fluid line 55 may be provided, through which steam may be delivered, through the filter presses and certain associated connections. If it is desired to recycle the oil, this may be done as by a connection 56 having valved branches 56a, 56b and 5E0 associated respectively with the three filter presses F F and FL The line 56 may be extended for recirculation of oil to the mixing vessel M above described.

A control panel generally indicated at P is desirably associated with the system, various control and gauge lines being extended therefrom to various parts of the equipment, as is indicated in dotted lines in Figure 3. These control and/or, gauge lines need not be considered in detail here-I.

in, although it is mentioned that for continuous,

7 operation it is contemplated that the control system shall incorporate flow controls, level con trols, etc., as will be understood by those skilled in the art.

The manner of use of the three filter presses illustrated in Figure 3 is the same as that described above with respect to Figure 1 and that description therefore need not be repeated.

With regard to the initial introduction of fresh adsorbent or clay from the tank S shown at the left of Figure 3, it is mentioned that this is of advantage under certain conditions, especially where the oil being treated tends to deposit gums or other material in the filter press being used for the first stage bleaching operation. The initial introduction of a small quantity or adsorbent when treating oils of this type provides for a continuous slight build-up of the filter cake in the filter press and thereby tends to prevent clogging of the press as a result of deposit of gums or other difficultly filterable material.

If the oil is suificiently clean so that tendency to clog the filter press does not occur, the initial addition of adsorbent may be dispensed with, as in the system of Figure 1. In this event, only two spray chambers may be needed in the treatment column, as is-also shown in the system of Figure 1. However, the system of Figure 3 may be utilized where a tendency to clog the first filter press is encountered, the spraying or stripping treatments in chambers and 4| serving to separate air and moisture from the adsorbent as well as from the oil, so that in the subsequent stages of treatment, during which the oil is retained, at relatively high temperature, the processing is eifected in the absence of any substantial quantity of air or moisture.

With respect to bleaching temperatures to be employed it may be said that temperatures generally recognized in this art as being appropriate or effective may be used in both bleaching stages of the method herein disclosed. The temperature, of course, will vary with different oils. Thus, with most of the fatty oils, such as cottonseed, soybean, peanut, corn, sunflower seed, sesame, and coconut, temperatures from about 200 F. to about 275 F. are suitable. In the case of palm oil, the temperature required may be as high as 300 F. to 350 F.

Various fats, for instance lard, tallows and animal greases may also be treated. Such fats, being esters, behave similarly to fatty oils, and are considered herein as coming within the term fatty oils. Appropriate temperatures of treating the fats lie in the same range (200 F. to 275 F.) applicable to most fatty oils.

Petroleum oils ordinarily require somewhat higher temperatures than the majority of the fatty oils, for instance from about 300 F. to 400 F.

I claim:

1. A method for bleaching oils including a first step comprising passing the oil at elevated temperature through a mass of partially spent bleaching adsorbent to partially bleach the oil, intermixing the partially bleached oil with fresh adsorbent to eifect further bleaching, spraying the mixture into a treatment zone at low pressure, separating the adsorbent from the oil after the spraying by introducing the admixture of oil and adsorbent into a filter to develop a mass of partially spent bleaching adsorbent, and utilizing said mass of partially spent adsorbent in situ in. said filter in partially bleaching additional oil according to said first step of the method.

2. A method according to claim 1' in which the mixture of oil and fresh adsorbent is heated prior to said spraying to a temperature efiective to release bound moisture in the fresh adsorbent.

3. A method for bleaching oils including initially subjecting the oil to steam stripping in a zone at low pressure in the presence of fresh adsorbent in admixture with the oil to separate air and moisture from both the oil and said adsorbent, passing the mixture of oil and adsorbent at elevated temperature through a mass of partially spent bleaching adsorbent to partially bleach the oil and concurrently filter out said fresh adsorbent, intermixing the partially bleached oil with fresh adsorbent to effect further bleaching, separating the adsorbent from the oil, and passing additional oil through a mass of the separated partially spent adsorbent to partially bleach said additional oil according to said first bleaching step of the method.

4. A method according to claim 3 in which the mixture of partially bleached oil and fresh adsorbent is sprayed at elevated temperature into a zone at low pressure before the adsorbent is separated from the mixture, to eifect release of bound moisture from the fresh adsorbent prior to separation and the subsequent reuse thereof.

5. A method for bleaching oils including a first bleaching step comprising passing the oil at elevated temperature through a mass of partially spent bleaching adsorbent to partially bleach the oil, intermixing the partially bleached oil with deaerated fresh adsorbent to effect further bleaching, treating the mixture at elevated temperature to separate bound moisture from the adsorbent, separating the adsorbent from the oil, and passing additional oil through a mass of the separated partially spent adsorbent to partially bleach said additional oil according to said first bleaching step of the method.

6. A multi-stage oil bleaching treatment comprising as one treatment stage passing oil at a bleaching temperature through a massed body of partially spent adsorbent to partially bleach the oil; as a subsequent treatment stage subjecting said partially bleached oil at a bleaching temperature to the bleaching action of adsorbent dispersed in the oil, thereby partially expending said dispersed adsorbent; separating said partially spent adsorbent from the oil treated in said subsequent treatment stage; and passing additional oil through a massed body of said separated partially spent adsorbent according to the first recited treatment stage.

7. A method according to claim 6 in which the separation of the partially spent adsorbent is effected by passing the partially bleached oil through a filter to develop a cake of adsorbent therein, and in which said cake is used in situ in the filter as said massed body of adsorbent in effecting the first recited treatment stage.

ALTON E. BAJLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

6. A MULTI-STAGE OIL BLEACHING TREATMENT COMPRISING AS ONE TREATMENT STAGE PASSING OIL AT A BLEACHING TEMPERATURE THROUGH A MASSED BODY OF PARTIALLY SPENT ADSORBENT TO PARTIALLY BLEACH THE OIL; AS A SUBSEQUENT TREATMENT STAGE SUBJECTING SAID PARTIALLY BLEACHED OIL AT A BLEACHING TEMPERATURE TO THE BLEACHING ACTION OF ADSORBENT DISPERSED IN THE OIL, THEREBY PARTIALLY EXPENDING SAID DISPERSED ADSORBENT:SEPARATING SAID PARTIALLY SPENT ADSORBENT FROM THE OIL TREATED IN SAID SUBSEQUENT TREATMENT STAGE; AND PASSING ADDITIONAL OIL THROUGH A MASSED BODY OF SAID SEPARATED PARTIALLY SPENT ADSORBENT ACCORDING TO THE FIRST RECITED TREATMENT STAGE. 